Study On Purification Effect And Its Mechanism Of Vegetative Filter Strips On Non-point Source Pollutants

With the rapid point source pollution control technology matures,non-point source pollution has become the important source of water environment pollution.There are many measures to control non-point source pollution,the one is the vegetative filter strips(VFS),a cheap and practical ecological engineering measure.VFS can effectively intercept runoff but also reduce pollutants of overland runoff.Repeated experiments on runoff simulation have been conducted in the field experiment base.Purification effects of non-point source pollutants of overland runoff by VFS have been analyzed under the different vegetation cover,inflow rate of runoff,initial soil water content and pollutant concentration of inflow.Purification mechanism of pollutants by VFS has been discussed.Interception effectiveness of sediment by VFS has been simulated by VFSMOD model.The main results are as follows:(1)The trend of concentration of coarse sediment under the VFS is declined along the flow.VFS has superior interception effectiveness to coarse sediment of 250.00-1000.00?m.This sediment was intercepted in the first 3.5m of VFS.There was a quadratic function between the coarse sediment concentration and the median diameter of coarse sediment.The diameter of coarse sediment of overland runoff is declined along the flow.VFS has better interception effectiveness for coarse sediment.(2)The study found that each VFS has better reduction effectiveness for fine sediment and lambda-cyhalothrin of overland runoff.The reduction rate of fine sediment and lambda-cyhalothrin concentration by VFS in overland runoff reach 80.3%and 47.15%,respectively,and the load reduction effectiveness of pollutants reach 85.59%and 63.56%,respectively.The purification efficiency of non-point source pollutants by VFS was influenced by vegetation cover,inflow rate of runoff,initial soil water content and pollutant concentration of inflow.The variation of inflow rate has prominent influence on the reduction effectiveness of pollutants by VFS in which Seabuckthorn and herb have grown.The variation of initial soil water content has remarkable influence on the reduction effectiveness of pollutants by grass filter strips.(3)VFS that has higher vegetation cover and biomass has better purification effect for non-point source pollutants of overland runoff under the same length of each VFS.There was a linear correlation relationship between the retention rate of runoff and the interception rate of sediment by VFS.The reduction rate of lambda-cyhalothrin concentration in runoff was logarithmically related with the distance along the flow and the runoff retentiont rate.(4)The interception effectiveness of sediments by VFS was simulated by VFSMOD model.It is found that the higher simulation precision using the VFSMOD model is for the sediment interception rate of by VFS is higher.The simulation values by VFSMOD are in agreement with the calculated experimental values.